U.S. Pat. No. 3,803,034 to A. G. Dasch describes the problems associated with the loss of fluidity of hydrocarbon oils at low temperatures and distinguishes the class of materials known in the petroleum art as middle distillate fuels. It also describes certain terpolymers for use as pour point depressants in hydrocarbon oils. The subject terpolymers of the patent are composed of (1) an olefin illustrated by ethylene, (2) an arylalkylene illustrated by styrene and (3) an unsaturated ester illustrated by (I) vinyl acetate and (II) methyl methacrylate.
No pour point data are given in the patent for ethylene-styrene-vinyl acetate terpolymers. However, the terpolymers described in that patent do not appear to be satisfactorily effective or efficient when used in the middle distillate fuel oil subclass of hydrocarbon oils such as No. 2 fuel oil.
Accordingly, an object of this invention is to provide improved pour point depressants. A particular object is to provide such improved pour point depressants for middle distillate fuels. Another object is to provide such improved pour point depressants for middle distillate fuels which are effective at lower concentration and are thus more efficient. Other objects and advantages of the invention will be apparent in the description that follows.